Physics - Elasticity Question with Solution | TestHub

$Y=\frac{F/A}{\frac{\Delta l}{l}}$ $\therefore F=\frac{YA}{l}\cdot \Delta l=k\cdot \Delta l$ Force $\propto$ extension If the extension is $x$, work done in extending by $dx$ $\therefore F=\frac{YA}{l}\cdot \Delta l=k\cdot \Delta l$ If $x$ is $\left(l^{\prime }-l\right),W=\frac{1}{2}k{\left(l^{\prime }-l\right)}^2$ i.e. work done is $\frac{1}{2}\frac{YA}{l}{\left(l-l^{\prime }\right)}^2$.